System and method for plasma-mediated modification of tissue

ABSTRACT

A method for cataract surgery on an eye of a patient includes scanning a first focus position of a first pulsed laser beam at a first pulse energy of between one-half microjoule and 50 microjoules in a first scanning pattern to photodisrupt a first tissue structure portion with a plurality of pulses of the first laser beam to form an incised surface; and afterwards, scanning a second focus position of a second pulsed laser beam having a second pulse energy being between 50 microjoules and 5,000 microjoules in a second scanning pattern that is co-registered to the first scanning pattern to further photodisrupt the same first tissue structure portion with the second laser beam to further separate segments of the first tissue structure along the incised surface.

RELATED APPLICATION DATA

The present application is a continuation of U.S. patent applicationSer. No. 13/023,483, filed Feb. 8, 2011, which claims the benefit under35 U.S.C. §119 to U.S. provisional application Ser. No. 61/302,437 filedon Feb. 8, 2010. The foregoing application is hereby incorporated byreference into the present application in its entirety.

FIELD

The present invention relates to ophthalmic surgical procedures andsystems, especially cataract surgery of the crystalline lens.

BACKGROUND

Cataract extraction is one of the most commonly performed surgicalprocedures in the world with estimated 2.5 million cases performedannually in the United States and 9.1 million cases worldwide in 2000.This was expected to increase to approximately 13.3 million estimatedglobal cases in 2006. This market is composed of various segmentsincluding intraocular lenses for implantation, viscoelastic polymers tofacilitate surgical maneuvers, disposable instrumentation includingultrasonic phacoemulsification tips, tubing, and various knives andforceps. Modern cataract surgery is typically performed using atechnique termed phacoemulsification in which an ultrasonic tip with anassociated water stream for cooling purposes is used to sculpt therelatively hard nucleus of the lens after performance of an opening inthe anterior lens capsule termed anterior capsulotomy or more recentlycapsulorhexis. Following these steps as well as removal of residualsofter lens cortex by aspiration methods without fragmentation, asynthetic foldable intraocular lens (IOL) is inserted into the eyethrough a small incision.

One of the earliest and most critical steps in the procedure is theperformance of capsulorhexis. This step evolved from an earliertechnique termed can-opener capsulotomy in which a sharp needle was usedto perforate the anterior lens capsule in a circular fashion followed bythe removal of a circular fragment of lens capsule typically in therange of 5-8 mm in diameter. This facilitated the next step of nuclearsculpting by phacoemulsification. Due to a variety of complicationsassociated with the initial can-opener technique, attempts were made byleading experts in the field to develop a better technique for removalof the anterior lens capsule preceding the emulsification step. Theconcept of the Continuous Curvilinear Capsulorhexis (CCC) is to providea smooth continuous circular opening through which not only thephacoemulsification of the nucleus can be performed safely and easily,but also for easy insertion of the intraocular lens. It provides both aclear central access for insertion, a permanent aperture fortransmission of the image to the retina by the patient, and also asupport of the IOL inside the remaining capsule that would limit thepotential for dislocation. Subsequent to the step of anterior CCC, andprior to IOL insertion the steps of hydrodissection, hydrodilineationand phaco emulsification occur. These are intended to identify andsoften the nucleus for the purposes of removal from the eye. These arethe longest and thought to be the most dangerous step in the proceduredue to the mechanical manipulation and the use of pulses of ultrasoundthat may lead to inadvertent ruptures of the posterior lens capsule,posterior dislocation of lens fragments, and potential damage anteriorlyto the corneal endothelium and/or iris and other delicate intraocularstructures. The central nucleus of the lens, which undergoes the mostopacification and thereby the most visual impairment, is structurallythe hardest and requires special techniques. A variety of surgicalmaneuvers employing ultrasonic fragmentation and also requiringconsiderable technical dexterity on the part of the surgeon haveevolved, including sculpting, cracking and chopping of the lens, theso-called “divide and conquer technique” and a whole host of similarlycreatively named techniques, such as phaco chop, etc. These are allsubject to the usual complications associated with delicate intraocularmaneuvers. Similar limitations exist in other ophthalmic procedures forwhich the present invention is particularly suited.

What is needed are ophthalmic methods, techniques and apparatus toadvance the standard of care of cataract and other ophthalmicpathologies.

SUMMARY

The aforementioned problems and needs are addressed by providing amethod of treating a lens of a patient using various scanned patterns ofoptical energy, especially to soften and/or segment the crystalline lensfor removal.

One embodiment is directed to a system for cataract surgery on an eye ofa patient, comprising: a first laser source configured to deliver afirst laser beam in a pulsed form at a first pulse energy; a secondlaser source configured to deliver a second laser beam in a pulsed format a second pulse energy greater than the first pulse energy; anscanning optical system, configured to: receive the first and secondlaser beams; and adjust a first focus position of the first laser beam,and a second focus position of the second laser beam, in up to threedimensions to direct the first and second laser beams onto one or moretargeted tissue structure portions of the eye of the patient; acontroller operatively coupled to the scanning optical system andconfigured to cause the scanning optical system to adjust the firstfocus position to photodisrupt a first tissue structure portion with thefirst laser beam, and subsequently adjust the second focus position tofurther photodisrupt the first tissue structure portion with the secondlaser beam. The first pulse energy may be between about one-halfmicrojoule and about 50 microjoules. The second pulse energy may bebetween about 50 microjoules and about 5,000 microjoules. The firstlaser source may be configured to produce laser pulses having a firstpulse duration between about 100 femtoseconds and about 10 picoseconds.The second laser source may be configured to produce laser pulses havinga second pulse duration between about 10 picoseconds and about 10nanoseconds. The controller may be configured to control the opticalsystem to direct the first and second laser beams based upon apredetermined treatment pattern. The first tissue structure portion maybe a portion of a crystalline lens of the eye. The controller may beoperatively coupled to the first and second laser sources, andconfigured to control the first and second pulse energies. Thepredetermined pattern may be selected to divide the lens into two ormore discrete segments. The predetermined pattern may comprise athree-dimensional pattern wherein two or more pulses are targeted fortwo or more different depths within the targeted tissue structureportion. The predetermined pattern may comprise a first grouping ofpulses to be directed to the targeted tissue structure portion, and asecond grouping of pulses to be directed to the targeted tissuestructure portion, such that the first grouping is comprised of asubstantially distinct range of pulse energies relative to the secondgrouping. The first grouping may comprise a relatively low pulse energyand the second grouping may comprise a relatively high pulse energy. Thefirst grouping may be directed to the targeted tissue structure portionbefore the second grouping. The first grouping may be directed to adeeper portion of the targeted tissue structure portion than the secondgrouping. The system may further comprise a third grouping directed tothe targeted tissue structure portion at a depth different than that ofthe first or second groupings.

Another embodiment is directed to a method of laser cataract surgery onan eye of a patient, comprising: positioning a three-dimensional laserirradiation pattern relative to one or more tissue structures of theeye; irradiating, with a pulsed laser source at a first pulse energy inaccordance with the pattern, one or more targeted portions of the one ormore tissue structures of the eye; irradiating again, with the pulsedlaser source at a second pulse energy higher than the first pulse energyin accordance with the pattern, the one or more targeted portions of theone or more tissue structures of the eye.

Another embodiment is directed to a method of treating a lens of apatient's eye includes generating a light beam, deflecting the lightbeam using a scanner to form a treatment pattern of the light beam,delivering the treatment pattern to the lens of a patient's eye tocreate a plurality of cuts in the lens in the form of the treatmentpattern to break the lens up into a plurality of pieces, and removingthe lens pieces from the patient's eye.

Another embodiment is directed to a method of treating a lens of apatient's eye that includes generating a light beam, deflecting thelight beam using a scanner to form a treatment pattern of the lightbeam, delivering the treatment pattern to the lens of a patient's eye tocreate a plurality of cuts in the lens in the form of the treatmentpattern, mechanically breaking the lens into a plurality of pieces alongthe cuts, and removing the lens pieces from the patient's eye.

Another embodiment is directed to a system that includes an imagingsystem configured to capture signals from a targeted tissue structure.The signals may be utilized to create an image of pertinent tissuestructures, and may be utilized as an input to the controller incontrolling the first and second laser sources and/or focal positions ofthe pertinent first and second laser beams. The first and second lasersources may comprise the same laser source.

Other objects and features of the present invention will become apparentby a review of the specification, claims and appended figures.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of the optical beam scanning system.

FIG. 2 is an optical diagram showing an alternative beam combiningscheme.

FIG. 3 is a schematic diagram of the optical beam scanning system withan alternative OCT configuration.

FIG. 4 is a schematic diagram of the optical beam scanning system withanother alternative OCT combining scheme.

FIGS. 5A-5C are side cross sectional views of the lens of the eyeillustrating various treatment zones.

FIGS. 6A-6C are top views of an eye lens illustrating variousconfigurations of line cuts.

FIG. 7 is a perspective three-dimensional view of the eye lensillustrating inclined plane cuts within the lens.

FIG. 8A is a side view of the eye lens illustrating non-inclined planecuts within the lens.

FIG. 8B is a side view of the eye lens illustrating inclined plane cutswithin the lens.

FIG. 9 is a perspective three-dimensional view of the eye lensillustrating inclined plane cuts within the lens forming apyramid-shaped lens segment.

FIG. 10 is a top view of an eye lens illustrating a cross-shapedsegmentation pattern.

FIGS. 11A-11B are top views of an eye lens illustrating differentconfigurations of a combination of linear and circular cuts.

FIG. 12 is a top view of an eye lens illustrating a spiral shaped cut.

FIG. 13 is a top view of an eye lens illustrating an array ofrectangular planar cuts.

FIG. 14 is a top view of an eye lens illustrating segmentation intoquadrants.

FIG. 15 is a top view of an eye lens illustrating softening cuts madeinto a lens quadrant.

FIGS. 16-19 are top views of an eye lens illustrating variouscombinations of an array of rectangular planar cuts and one or more linecuts.

FIG. 20 illustrates a top view of an eye lens illustrating a treatmentparadigm wherein a plurality of pulses is utilized to form orthogonalcuts.

FIG. 21 illustrates a top view of an eye lens illustrating a treatmentparadigm wherein a plurality of pulses is utilized to form orthogonalcuts.

FIG. 22 illustrates a side view of an eye lens illustrating a treatmentparadigm wherein pulses of varied energy are utilized in lenssegmentation.

FIG. 23 illustrates a side view of an eye lens illustrating a treatmentparadigm wherein pulses of varied energy are utilized in lenssegmentation.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

The present invention can be implemented by a system that projects orscans an optical beam into a patient's eye 68, such as system 2 shown inFIG. 1 which includes an ultrafast (UF) light source 4 (e.g. afemtosecond laser, or a dual purpose system capable of emitting pulsesin a lower and in a higher range of pulse energies, perhaps withdifferent pulse durations.). Using this system, a beam may be scanned ina patient's eye in three dimensions: X, Y, Z. In this embodiment, the UFwavelength can vary between 1010 nm to 1100 nm and the pulse width canvary from 100 fs to 10000 fs. The pulse repetition frequency can alsovary from 10 kHz to 250 kHz. Safety limits with regard to unintendeddamage to non-targeted tissue bound the upper limit with regard torepetition rate and pulse energy; while threshold energy, time tocomplete the procedure and stability bound the lower limit for pulseenergy and repetition rate. The peak power of the focused spot in theeye 68 and specifically within the crystalline lens 69 and anteriorcapsule of the eye is sufficient to produce optical breakdown andinitiate a plasma-mediated ablation process. Near-infrared wavelengthsare preferred because linear optical absorption and scattering inbiological tissue is reduced across that spectral range. As an example,laser 4 may be a repetitively pulsed 1035 nm device that produces 500 fspulses at a repetition rate of 100 kHz and an individual pulse energy inthe ten microjoule range. Although not illustrated, UF Light Source 4may be further configured to provide higher energy pulses with the sameor longer pulse durations than those exiting the system after pulsecompression. That is, the un-compressed beam may be extracted from UFLight Source 4 in order to provide those higher energy pulses.Regardless, the following system description details means to achievethe usage of higher and/or lower energy pulses.

The laser 4 is controlled by control electronics 300, via an input andoutput device 302, to create optical beam 6. Control electronics 300 maybe a computer, microcontroller, etc. In this example, the entire systemis controlled by the controller 300, and data moved through input/outputdevice IO 302. A graphical user interface GUI 304 may be used to setsystem operating parameters, process user input (UI) 306 on the GUI 304,and display gathered information such as images of ocular structures.

The generated UF light beam 6 proceeds towards the patient eye 68passing through half-wave plate, 8, and linear polarizer, 10. Thepolarization state of the beam can be adjusted so that the desiredamount of light passes through half-wave plate 8 and linear polarizer10, which together act as a variable attenuator for the UF beam 6.Additionally, the orientation of linear polarizer 10 determines theincident polarization state incident upon beamcombiner 34, therebyoptimizing beamcombiner throughput.

The UF beam proceeds through a shutter 12, aperture 14, and a pickoffdevice 16. The system controlled shutter 12 ensures on/off control ofthe laser for procedural and safety reasons. The aperture sets an outeruseful diameter for the laser beam and the pickoff monitors the outputof the useful beam. The pickoff device 16 includes of a partiallyreflecting mirror 20 and a detector 18. Pulse energy, average power, ora combination may be measured using detector 18. The information can beused for feedback to the half-wave plate 8 for attenuation and to verifywhether the shutter 12 is open or closed. In addition, the shutter 12may have position sensors to provide a redundant state detection.

The beam passes through a beam conditioning stage 22, in which beamparameters such as beam diameter, divergence, circularity, andastigmatism can be modified. In this illustrative example, the beamconditioning stage 22 includes a 2 element beam expanding telescopecomprised of spherical optics 24 and 26 in order to achieve the intendedbeam size and collimation. Although not illustrated here, an anamorphicor other optical system can be used to achieve the desired beamparameters. The factors used to determine these beam parameters includethe output beam parameters of the laser, the overall magnification ofthe system, and the desired numerical aperture (NA) at the treatmentlocation. In addition, the optical system 22 can be used to imageaperture 14 to a desired location (e.g. the center location between the2-axis scanning device 50 described below). In this way, the amount oflight that makes it through the aperture 14 is assured to make itthrough the scanning system. Pickoff device 16 is then a reliablemeasure of the usable light.

After exiting conditioning stage 22, beam 6 reflects off of fold mirrors28, 30, & 32. These mirrors can be adjustable for alignment purposes.The beam 6 is then incident upon beam combiner 34. Beamcombiner 34reflects the UF beam 6 (and transmits both the OCT 114 and aim 202 beamsdescribed below). For efficient beamcombiner operation, the angle ofincidence is preferably kept below 45 degrees and the polarization wherepossible of the beams is fixed. For the UF beam 6, the orientation oflinear polarizer 10 provides fixed polarization.

Following the beam combiner 34, the beam 6 continues onto the z-adjustor Z scan device 40. In this illustrative example the z-adjust includesa Galilean telescope with two lens groups 42 and 44 (each lens groupincludes one or more lenses). Lens group 42 moves along the z-axis aboutthe collimation position of the telescope. In this way, the focusposition of the spot in the patient's eye 68 moves along the z-axis asindicated. In general there is a fixed linear relationship between themotion of lens 42 and the motion of the focus. In this case, thez-adjust telescope has an approximate 2× beam expansion ratio and a 1:1relationship of the movement of lens 42 to the movement of the focus.Alternatively, lens group 44 could be moved along the z-axis to actuatethe z-adjust, and scan. The z-adjust is the z-scan device for treatmentin the eye 68. It can be controlled automatically and dynamically by thesystem and selected to be independent or to interplay with the X-Y scandevice described next. Mirrors 36 and 38 can be used for aligning theoptical axis with the axis of z-adjust device 40.

After passing through the z-adjust device 40, the beam 6 is directed tothe x-y scan device by mirrors 46 & 48. Mirrors 46 & 48 can beadjustable for alignment purposes. X-Y scanning is achieved by thescanning device 50 preferably using two mirrors 52 & 54 under thecontrol of control electronics 300, which rotate in orthogonaldirections using motors, galvanometers, or any other well known opticmoving device. Mirrors 52 & 54 are located near the telecentric positionof the objective lens 58 and contact lens 66 combination describedbelow. Tilting these mirrors 52/54 causes them to deflect beam 6,causing lateral displacements in the plane of UF focus located in thepatient's eye 68. Objective lens 58 may be a complex multi-element lenselement, as shown, and represented by lenses 60, 62, and 64. Thecomplexity of the lens 58 will be dictated by the scan field size, thefocused spot size, the available working distance on both the proximaland distal sides of objective 58, as well as the amount of aberrationcontrol. An f-theta lens 58 of focal length 60 mm generating a spot sizeof 10 μm, over a field of 10 mm, with an input beam size of 15 mmdiameter is an example. Alternatively, X-Y scanning by scanner 50 may beachieved by using one or more moveable optical elements (e.g. lenses,gratings) which also may be controlled by control electronics 300, viainput and output device 302.

The aiming and treatment scan patterns can be automatically generated bythe scanner 50 under the control of controller 300. Such patterns may becomprised of a single spot of light, multiple spots of light, acontinuous pattern of light, multiple continuous patterns of light,and/or any combination of these. In addition, the aiming pattern (usingaim beam 202 described below) need not be identical to the treatmentpattern (using light beam 6), but preferably at least defines itsboundaries in order to assure that the treatment light is delivered onlywithin the desired target area for patient safety. This may be done, forexample, by having the aiming pattern provide an outline of the intendedtreatment pattern. This way the spatial extent of the treatment patternmay be made known to the user, if not the exact locations of theindividual spots themselves, and the scanning thus optimized for speed,efficiency and accuracy. The aiming pattern may also be made to beperceived as blinking in order to further enhance its visibility to theuser.

An optional contact lens 66, which can be any suitable ophthalmic lens,can be used to help further focus the optical beam 6 into the patient'seye 68 while helping to stabilize eye position. The positioning andcharacter of optical beam 6 and/or the scan pattern the beam 6 forms onthe eye 68 may be further controlled by use of an input device such as ajoystick, or any other appropriate user input device (e.g. GUI 304) toposition the patient and/or the optical system.

The UF laser 4 and controller 300 can be set to target the surfaces ofthe targeted structures in the eye 68 and ensure that the beam 6 will befocused where appropriate and not unintentionally damage non-targetedtissue. Imaging modalities and techniques described herein, such as forexample, Optical Coherence Tomography (OCT), Purkinje imaging,Scheimpflug imaging, or ultrasound may be used to determine the locationand measure the thickness of the lens and lens capsule to providegreater precision to the laser focusing methods, including 2D and 3Dpatterning. Laser focusing may also be accomplished using one or moremethods including direct observation of an aiming beam, OpticalCoherence Tomography (OCT), Purkinje imaging, Scheimpflug imaging,ultrasound, or other known ophthalmic or medical imaging modalitiesand/or combinations thereof. In the embodiment of FIG. 1, an OCT device100 is described, although other modalities are within the scope of thepresent invention. An OCT scan of the eye will provide information aboutthe axial location of the anterior and posterior lens capsule, theboundaries of the cataract nucleus, as well as the depth of the anteriorchamber. This information is then be loaded into the control electronics300, and used to program and control the subsequent laser-assistedsurgical procedure. The information may also be used to determine a widevariety of parameters related to the procedure such as, for example, theupper and lower axial limits of the focal planes used for cutting thelens capsule and segmentation of the lens cortex and nucleus, and thethickness of the lens capsule among others.

The OCT device 100 in FIG. 1 includes a broadband or a swept lightsource 102 that is split by a fiber coupler 104 into a reference arm 106and a sample arm 110. The reference arm 106 includes a module 108containing a reference reflection along with suitable dispersion andpath length compensation. The sample arm 110 of the OCT device 100 hasan output connector 112 that serves as an interface to the rest of theUF laser system. The return signals from both the reference and samplearms 106, 110 are then directed by coupler 104 to a detection device128, which employs either time domain, frequency or single pointdetection techniques. In FIG. 1, a frequency domain technique is usedwith an OCT wavelength of 920 nm and bandwidth of 100 nm.

Exiting connector 112, the OCT beam 114 is collimated using lens 116.The size of the collimated beam 114 is determined by the focal length oflens 116. The size of the beam 114 is dictated by the desired NA at thefocus in the eye and the magnification of the beam train leading to theeye 68. Generally, OCT beam 114 does not require as high an NA as the UFbeam 6 in the focal plane and therefore the OCT beam 114 is smaller indiameter than the UF beam 6 at the beamcombiner 34 location. Followingcollimating lens 116 is aperture 118 which further modifies theresultant NA of the OCT beam 114 at the eye. The diameter of aperture118 is chosen to optimize OCT light incident on the target tissue andthe strength of the return signal. Polarization control element 120,which may be active or dynamic, is used to compensate for polarizationstate changes which may be induced by individual differences in cornealbirefringence, for example. Mirrors 122 & 124 are then used to directthe OCT beam 114 towards beamcombiners 126 & 34. Mirrors 122 & 124 maybe adjustable for alignment purposes and in particular for overlaying ofOCT beam 114 to UF beam 6 subsequent to beamcombiner 34. Similarly,beamcombiner 126 is used to combine the OCT beam 114 with the aim beam202 described below.

Once combined with the UF beam 6 subsequent to beamcombiner 34, OCT beam114 follows the same path as UF beam 6 through the rest of the system.In this way, OCT beam 114 is indicative of the location of UF beam 6.OCT beam 114 passes through the z-scan 40 and x-y scan 50 devices thenthe objective lens 58, contact lens 66 and on into the eye 68.Reflections and scatter off of structures within the eye provide returnbeams that retrace back through the optical system, into connector 112,through coupler 104, and to OCT detector 128. These return backreflections provide the OCT signals that are in turn interpreted by thesystem as to the location in X, Y Z of UF beam 6 focal location.

OCT device 100 works on the principle of measuring differences inoptical path length between its reference and sample arms. Therefore,passing the OCT through z-adjust 40 does not extend the z-range of OCTsystem 100 because the optical path length does not change as a functionof movement of 42. OCT system 100 has an inherent z-range that isrelated to the detection scheme, and in the case of frequency domaindetection it is specifically related to the spectrometer and thelocation of the reference aim 106. In the case of OCT system 100 used inFIG. 1, the z-range is approximately 1-2 mm in an aqueous environment.Extending this range to at least 4 mm involves the adjustment of thepath length of the reference arm within OCT system 100. Passing the OCTbeam 114 in the sample arm through the z-scan of z-adjust 40 allows foroptimization of the OCT signal strength. This is accomplished byfocusing the OCT beam 114 onto the targeted structure whileaccommodating the extended optical path length by commensuratelyincreasing the path within the reference aim 106 of OCT system 100.

Because of the fundamental differences in the OCT measurement withrespect to the UF focus device due to influences such as immersionindex, refraction, and aberration, both chromatic and monochromatic,care must be taken in analyzing the OCT signal with respect to the UFbeam focal location. A calibration or registration procedure as afunction of X, Y Z should be conducted in order to match the OCT signalinformation to the UF focus location and also to the relate to absolutedimensional quantities.

Observation of an aim beam may also be used to assist the user todirecting the UF laser focus. Additionally, an aim beam visible to theunaided eye in lieu of the infrared OCT and UF beams can be helpful withalignment provided the aim beam accurately represents the infrared beamparameters. An aim subsystem 200 is employed in the configuration shownin FIG. 1. The aim beam 202 is generated by a an aim beam light source201, such as a helium-neon laser operating at a wavelength of 633 nm.Alternatively a laser diode in the 630-650 nm range could be used. Theadvantage of using the helium neon 633 nm beam is its long coherencelength, which would enable the use of the aim path as a laser unequalpath interferometer (LUPI) to measure the optical quality of the beamtrain, for example.

Once the aim beam light source generates aim beam 202, the aim beam 202is collimated using lens 204. The size of the collimated beam isdetermined by the focal length of lens 204. The size of the aim beam 202is dictated by the desired NA at the focus in the eye and themagnification of the beam train leading to the eye 68. Generally, aimbeam 202 should have close to the same NA as UF beam 6 in the focalplane and therefore aim beam 202 is of similar diameter to the UF beamat the beamcombiner 34 location. Because the aim beam is meant tostand-in for the UF beam 6 during system alignment to the target tissueof the eye, much of the aim path mimics the UF path as describedpreviously. The aim beam 202 proceeds through a half-wave plate 206 andlinear polarizer 208. The polarization state of the aim beam 202 can beadjusted so that the desired amount of light passes through polarizer208. Elements 206 & 208 therefore act as a variable attenuator for theaim beam 202. Additionally, the orientation of polarizer 208 determinesthe incident polarization state incident upon beamcombiners 126 and 34,thereby fixing the polarization state and allowing for optimization ofthe beamcombiners' throughput. Of course, if a semiconductor laser isused as aim beam light source 200, the drive current can be varied toadjust the optical power.

The aim beam 202 proceeds through a shutter 210 and aperture 212. Thesystem controlled shutter 210 provides on/off control of the aim beam202. The aperture 212 sets an outer useful diameter for the aim beam 202and can be adjusted appropriately. A calibration procedure measuring theoutput of the aim beam 202 at the eye can be used to set the attenuationof aim beam 202 via control of polarizer 206.

The aim beam 202 next passes through a beam conditioning device 214.Beam parameters such as beam diameter, divergence, circularity, andastigmatism can be modified using one or more well known beamingconditioning optical elements. In the case of an aim beam 202 emergingfrom an optical fiber, the beam conditioning device 214 can simplyinclude a beam expanding telescope with two optical elements 216 and 218in order to achieve the intended beam size and collimation. The finalfactors used to determine the aim beam parameters such as degree ofcollimation are dictated by what is necessary to match the UF beam 6 andaim beam 202 at the location of the eye 68. Chromatic differences can betaken into account by appropriate adjustments of beam conditioningdevice 214. In addition, the optical system 214 is used to imageaperture 212 to a desired location such as a conjugate location ofaperture 14.

The aim beam 202 next reflects off of fold mirrors 222 & 220, which arepreferably adjustable for alignment registration to UF beam 6 subsequentto beam combiner 34. The aim beam 202 is then incident upon beamcombiner 126 where the aim beam 202 is combined with OCT beam 114.Beamcombiner 126 reflects the aim beam 202 and transmits the OCT beam114, which allows for efficient operation of the beamcombining functionsat both wavelength ranges. Alternatively, the transmit and reflectfunctions of beamcombiner 126 can be reversed and the configurationinverted. Subsequent to beamcombiner 126, aim beam 202 along with OCTbeam 114 is combined with UF beam 6 by beamcombiner 34.

A device for imaging the target tissue on or within the eye 68 is shownschematically in FIG. 1 as imaging system 71. Imaging system includes acamera 74 and an illumination light source 86 for creating an image ofthe target tissue. The imaging system 71 gathers images which may beused by the system controller 300 for providing pattern centering aboutor within a predefined structure. The illumination light source 86 forthe viewing is generally broadband and incoherent. For example, lightsource 86 can include multiple LEDs as shown. The wavelength of theviewing light source 86 is preferably in the range of 700 nm to 750 nm,but can be anything that is accommodated by the beamcombiner 56, whichcombines the viewing light with the beam path for UF beam 6 and aim beam202 (beamcombiner 56 reflects the viewing wavelengths while transmittingthe OCT and UF wavelengths). The beamcombiner 56 may partially transmitthe aim wavelength so that the aim beam 202 can be visible to theviewing camera 74. Optional polarization element 84 in front of lightsource 86 can be a linear polarizer, a quarter wave plate, a half-waveplate or any combination, and is used to optimize signal. A false colorimage as generated by the near infrared wavelength is acceptable.

The illumination light from light source 86 is directed down towards theeye using the same objective lens 58 and contact lens 66 as the UF andaim beam 6, 202. The light reflected and scattered off of variousstructures in the eye 68 are collected by the same lenses 58 & 66 anddirected back towards beamcombiner 56. There, the return light isdirected back into the viewing path via beam combiner and mirror 82, andon to camera 74. Camera 74 can be, for example but not limited to, anysilicon based detector array of the appropriately sized format. Videolens 76 forms an image onto the camera's detector array while opticalelements 80 & 78 provide polarization control and wavelength filteringrespectively. Aperture or iris 81 provides control of imaging NA andtherefore depth of focus and depth of field. A small aperture providesthe advantage of large depth of field which aids in the patient dockingprocedure. Alternatively, the illumination and camera paths can beswitched. Furthermore, aim light source 200 can be made to emit in theinfrared which would not directly visible, but could be captured anddisplayed using imaging system 71.

Coarse adjust registration is usually needed so that when the contactlens 66 comes into contact with the cornea, the targeted structures arein the capture range of the X, Y scan of the system. Therefore a dockingprocedure is preferred, which preferably takes in account patient motionas the system approaches the contact condition (i.e. contact between thepatient's eye 68 and the contact lens 66. The viewing system 71 isconfigured so that the depth of focus is large enough such that thepatient's eye 68 and other salient features may be seen before thecontact lens 66 makes contact with eye 68.

Preferably, a motion control system 70 is integrated into the overallcontrol system 2, and may move the patient, the system 2 or elementsthereof, or both, to achieve accurate and reliable contact betweencontact lens 66 and eye 68. Furthermore, a vacuum suction subsystem andflange may be incorporated into system 2, and used to stabilize eye 68.The alignment of eye 68 to system 2 via contact lens 66 may beaccomplished while monitoring the output of imaging system 71, andperformed manually or automatically by analyzing the images produced byimaging system 71 electronically by means of control electronics 300 viaIO 302. Force and/or pressure sensor feedback may also be used todiscern contact, as well as to initiate the vacuum subsystem.

An alternative beamcombining configuration is shown in the alternateembodiment of FIG. 2. For example, the passive beamcombiner 34 in FIG. 1can be replaced with an active combiner 140 in FIG. 2. The activebeamcombiner 34 can be a moving or dynamically controlled element suchas a galvanometric scanning mirror, as shown. Active combiner 140changes it angular orientation in order to direct either the UF beam 6or the combined aim and OCT beams 202,114 towards the scanner 50 andeventually eye 68 one at a time. The advantage of the active combiningtechnique is that it avoids the difficulty of combining beams withsimilar wavelength ranges or polarization states using a passive beamcombiner. This ability is traded off against the ability to havesimultaneous beams in time and potentially less accuracy and precisiondue to positional tolerances of active beam combiner 140.

Another alternate embodiment is shown in FIG. 3 which is similar to thatof FIG. 1 but utilizes an alternate approach to OCT 100. In FIG. 3, OCT101 is the same as OCT 100 in FIG. 1, except that the reference arm 106has been replaced by reference aim 132. This free-space OCT referencearm 132 is realized by including beamsplitter 130 after lens 116. Thereference beam 132 then proceeds through polarization controllingelement 134 and then onto the reference return module 136. The referencereturn module 136 contains the appropriate dispersion and path lengthadjusting and compensating elements and generates an appropriatereference signal for interference with the sample signal. The sample armof OCT 101 now originates subsequent to beamsplitter 130. The potentialadvantages of this free space configuration include separatepolarization control and maintenance of the reference and sample arms.The fiber based beam splitter 104 of OCT 101 can also be replaced by afiber based circulator. Alternately, both OCT detector 128 andbeamsplitter 130 might be moved together as opposed to reference arm136.

FIG. 4 shows another alternative embodiment for combining OCT beam 114and UF beam 6. In FIG. 4, OCT 156 (which can include either of theconfigurations of OCT 100 or 101) is configured such that its OCT beam154 is coupled to UF beam 6 after the z-scan 40 using beamcombiner 152.In this way, OCT beam 154 avoids using the z-adjust. This allows the OCT156 to possibly be folded into the beam more easily and shortening thepath length for more stable operation. This OCT configuration is at theexpense of an optimized signal return strength as discussed with respectto FIG. 1. There are many possibilities for the configuration of the OCTinterferometer, including time and frequency domain approaches, singleand dual beam methods, swept source, etc, as described in U.S. Pat. Nos.5,748,898; 5,748,352; 5,459,570; 6,111,645; and 6,053,613 (which areincorporated herein by reference.)

FIGS. 5 through 15 illustrate the various embodiments of the presentinvention. Specifically, they describe possible scanned 3-dimensionalpatterns within lens 69 of the patient's eye 68. These patterns havebeen specifically designed to provide more convenient splitting of lens69 into segments that are easy to aspirate using existing technology anddevices. Phacoemulsification is particularly well suited for this.Several such aspiration devices are commercially available and wellknown in the art.

FIG. 5A to 5C illustrate a side views of lens 69 and the depth profilesof the patterns of FIGS. 6 to 15. Specifically, in FIGS. 5A to 5C,treatment zone 500 denotes the internal volume of lens 69 where beam 6is used for softening the cataractous material within lens 69. Treatmentzone 500 has a high density of laser exposures, but a distinct safetyzone 502 in the lens 69 between the treatment zone 500 and the posteriorcapsular bag surface 514 is preferably maintained, to insure that thesurface 514 is not damaged by beam 6. The inner boundary of safety zone502 ranges between 10 μm to 1000 μm away from surface 514, but istypically 300 μm, and may be determined by use of OCT device 100 withinsystem 2. Safety zone 502 may also comprise the softer portions of lens69, the cortex and epi-nucleus. Safety zone 502 may also be a functionof the numerical aperture (NA) used for beams 6, 114 & 202 in system 2.The higher the NA used, the closer the focus of beam 6 from system 2 canbe to surface 514 without risk of incidental damage due to the increaseddivergence of beam 6. Damage to posterior surface 514 may cause surgicalcomplications, and retinal damage.

As shown in FIG. 5A, safety zone 502 is maintained throughout lens 69except opening 504 in anterior surface 512 of the capsule, as thatportion of the capsule will ultimately be removed.

FIG. 5B shows the example where treatment zone 500 extends in acylindrical shape of circular projection from the front (top) of lens69, with the addition of safety zone 503 adjacent to surface 512 inaddition to safety zone 502 for posterior surface 514.

FIG. 5C shows an alternate embodiment where treatment zone 500 extendsin a cylindrical shape and only safety zone 502 is used. This representsthe case where area 504 of anterior surface 512 will be incised andultimately removed, so safety zone 503 is not required.

In both FIGS. 5B and 5C, the diameter of the cylindrical treatment zone500 can be the same size as the capsular opening but also smaller orbigger than capsular opening 504. The safety zone 502 is used for“lens-in-the-bag” IOL implants. In the alternate case of a“bag-in-the-lens” approach, where the posterior capsule will also beincised and ultimately removed, incisions will be made by the system inposterior surface 514 and the safety zone 502 need not be used,similarly to the case of FIG. 5C.

In nearly all previously described ultrasonic phacoemulsificationtechniques, lens 69 is split into several smaller pieces to enableeasier handling of the single segments. Using optical segmentationpatterns enables pre-segmentation of the lens 69 into smaller piecesmore reliably and with better control than prior ultrasonic techniques.Exemplary optical segmentation patterns are shown in FIG. 6A to 6C, asseen from the front of the lens 69. Depending on its hardness, lens 69may be split into a variable number of segments, the number of segmentstypically, but not always, increasing with hardness. In the pattern ofFIG. 6A, the optical beam 6 is scanned in a pattern of two crossing cuts520, will is ideal for cataract grades 1-3 in order to split lens 69into four sections, or quadrants. For cataracts of grade 3+ and higher,a scanned pattern as shown in FIG. 6B having three crossing cuts 522 toform sextants is ideal. For the hardest cataracts of grade 4-4+, ascanned pattern of four crossing cuts 524 implementing octant splittingas shown in FIG. 6C would be ideal.

System 2 can also be configured to laterally shift the center point ofthe splitting patterns of FIG. 6A to 6C over depth, creating inclinedplanes of laser induced damage via beam 6. This is shown in FIG. 7,where the two laser cut planes 526 shift their crossing point 528throughout the depth of lens 69. This enables three dimensional inclinedplane cuts within the lens 69 that promote easier removal of thequadrants from the anterior side 527 of the lens 69, as the problem ofinterference of the posterior edges 529 is avoided. Furthermore, thesame benefits apply to the general case of any number of multipleaxi-symmetric intersecting cuts within the lens 69.

The difficulty of extracting lens segments 530 through the limitingaperture of the iris 532 without an inclined plane is depicted in FIG.8A. Without the ability to move laterally, the lens segment 530 will beblocked by the iris 532 due to anterior 527 and posterior 529interference with the remaining lens segments 533. FIG. 8B is a sideview of the inclined plane cuts described in FIG. 7. The inclined planesegment 536 can be removed through the iris 532 by sliding along thecontact plane 535 with the remaining inclined plane lens segments 537.

Another embodiment of lens segmentation is shown in FIG. 9 whichconsists of four inclined laser cut planes 536 merging in a manner tocreate a segment within lens 69 that is shaped similar to an invertedpyramid. This segment has its anterior portion 527 larger than itsposterior portion 529, thus allowing it to be more easily removed. Thissimplifies the removal of the remaining lens sections 537 which allowsfaster progress of the surgeon. Furthermore, the same benefits apply tothe general case of any number of multiple axi-symmetric intersectingcuts inclined in the same manner within the lens 69.

FIG. 10 illustrates a cross-shaped optical segmentation pattern 540which includes four cross bar quadrants 542. This pattern enablespre-formed channels which are used in the “divide and conquer” techniqueof phacoemulsification. This also allows easier splitting of the lenswith phacoemulsification by direct mechanical means. The width of thecross bar quadrants 542 is preferably selected to correspond to theouter width of the phacoemulsification tip 541 used by the surgeon. Atypically but not limiting example of tip widths includes 0.5 mm to 1.5mm. The small quadrant width can be chosen to be smaller than the innerdiameter of the phacoemulsification tip 541, such as between 0.3 mm and1.3 mm, for easier insertion of the tip and aspiration of lens material.

FIG. 11A illustrates another optical segmentation pattern similar tothat of FIGS. 5 & 6, which is especially useful in conditioning harderlens nuclei. FIG. 11A illustrates an optical segmentation patternsimilar to that of FIG. 6B, but with the addition of concentric circularscans/cuts 604 that serve to further divide the nucleus 600 of lens 69into segments small enough to be aspirated through a small probe andcommensurately small capsular incision. In this example, the crossedcuts 522 extend beyond the nucleus 600 of lens 69, passing throughnuclear boundary 601, and extending into the softer cortex and/orepi-nucleus of lens 69 that are inherently easy to remove via aspirationalone. Thus, by extending the laser segmentation pattern into the softermaterial surrounding nucleus 600, lens removal is further facilitated.The boundary 601 between nucleus 600 and the epi-nucleus or cortex oflens 69 may be determined via OCT device 100, and/or imaging system 71by mapping the target tissues and discerning changes in the opticalproperties of the tissue. More opaque material will be readily apparentto both imaging system 71 and OCT device 100. The spatial map of theirresponses may be used by CPU 300 to generate a boundary for nucleus 600,and guide the patterning to include all of nucleus 600 and theperipheral softer material.

FIG. 11B shows an optical segmentation pattern similar to that of FIG.11A, except that crossed cuts 522 do not pass through nucleus center602, as it's already small enough to be easily aspirated. This may savetime and cumulative energy delivered during a procedure, making it saferand more efficient.

FIG. 12 shows an alternate optical segmentation pattern in the form of a“carousel pattern.” The spiral shaped cut 608 of the “carousel” patternallows for the increased ease of aspiration by causing the hardenednucleus 600 of lens 69 to unroll when aspirated by phacoemulsificationtip 541, as indicated by direction R. The spiral spacing of the carouselpattern may be chosen to fit easily within phacoemulsification tip 541.Should the nucleus 600 be too stiff to easily unfurl along the spiralcut 608 of the carousel pattern, a series of sub-segment cuts 610 may beemployed to cause the hardened nucleus to break into segments smallenough to be easily aspirated by phacoemulsification tip 541. The widthof a single section should be made to be smaller than the inner-diameterof the phacoemulsification tip 541, typically but not limited toinner-diameters between 1.1 mm and 0.25 mm. Alternate, orthogonal planesmay also be cut into lens 69 to create smaller still segments of nucleus600 to assist with its removal, especially with very hard nuclei.

FIG. 13 shows an alternate optical segmentation pattern, with an arrayof rectangular planar cuts 520 (i.e. crossing array of rows and columnsof cuts) creating pattern 620 to facilitate removal of lens 69 bysegmenting it into rectangular sub-elements 618. This is shown asextending beyond the boundary 601 of the nucleus 600 (not explicitlyshown). As described above with respect to FIGS. 11A and B, the width ofa single section 618 should be made to be smaller than theinner-diameter of the phacoemulsification tip 541, typically but notlimited to inner-diameters between 1.1 mm and 0.25 mm. Orthogonal planes(i.e. cuts parallel to the anterior surface 512 of the capsule) may alsobe cut into lens 69 to create smaller still segments and further assistwith lens removal, especially with very hard nuclei.

FIG. 14 depicts lens segmentation into quadrants 622 by creating planarcrossed cuts 520 in the lens 69, together with softening cuts 618 withineach quadrant to better facilitate removal of the lens byphacoemulsification. This technique combines segmenting cuts 520 thatare larger (i.e. deeper, longer and/or generated with greater pulseenergy), with softening cuts 618 that are smaller (shallower, shorterand/or generated with less pulse energy). The distance between thesplitting and softening cuts are selected based on the hardness of thelens. The central plane cuts 520 allow the lens splitting forces topenetrate all the way out to the lens cortex, better assuring thereliable propagation of cracks along cuts 520. The spacing 624 betweenthe splitting cuts 520 and the softening pattern of cuts 618 may bevariable, but is typically but not limited to be between 0.1 mm to 1 mm.

FIG. 15 shows an another example of softening cuts, where each quadrant622 is filled with a regular array of single laser spots 626 that aredistributed throughout quadrant 622. Single laser spots 626 serve tosoften the material of the lens in order to facilitate its removal. Thepatterning of laser spots 626 need not be regular, as shown. It may be arandomized distribution of spots throughout the volume subtended byquadrant 622.

FIG. 16 depicts lens segmentation similar to that of FIGS. 13 & 14 withthe addition of pattern 620 of softening cuts being confined to thecenter of the lens and segmenting cuts 520 being provided to facilitatethe “bowl and chop” technique of phacoemsulification. The boundary ofpattern 620 is shown as circular, but may be any shape. The centralplane cuts 520 allow the lens splitting forces to penetrate all the wayout to the lens cortex, better assuring the reliable propagation ofcracks along cuts 520.

FIGS. 17 & 18 depict similar patterns to facilitate the “stop and chop”technique of phacoemsulification. The thickness of pattern 620 may bevariable, but is typically but not limited to be between 0.1 mm to 1 mm.The central plane cuts 520 allow the lens splitting forces to penetrateall the way out to the lens cortex, better assuring the reliablepropagation of cracks along cuts 520.

FIG. 19 depicts lens segmentation including central pattern 620 ofsoftening cuts and segmenting cuts 520 to facilitate the combined“divide and conquer” and “pre-chopping” techniques ofphacoemsulifcation. The meridonal thickness of pattern 620 may bevariable, but is typically but not limited to be between 0.1 mm to 1 mm.The central plane cuts 520 allow the lens splitting forces to penetrateall the way out to the lens cortex, better assuring the reliablepropagation of cracks along cuts 520.

For any pattern described above, the system 2 may also be made todeliver additional laser pulses or cuts to the incisions previouslycreated in the lens material. These pulses can create bubbles that mayserve to further separate the material for easier aspiration. Because itrequires less energy density to cause a bubble to form at an interface,these later pulses can be attenuated as compared to the initialsegmentation pulses. Furthermore, the laser beam may be made to lingerat a location for a time sufficient to produce a large bubble, forcingthe material to further separate. This can be done in a number ofdifferent ways. The system 2 may be configured to perform theseseparation pulses before, during and/or after a scan.

Preferably, the cataract lens is segmented into quadrants for removal.If the surgeon just starts to remove the central hard lens nucleus, theyare left with an annulus of lens material within the lens capsule. Thisannulus is extremely hard to remove due to the fact that it is locatedright under the iris that impairs or even inhibits the surgeon tovisualize it on the surgical microscope.

Conventionally, the surgical technique of divide-and-conquer techniquehas been developed to minimize surgical complications and to avoid thecreation of the lens annulus. After the manual capsulorhexis, thesurgeon uses the phacoemulsification system to sculpture twoperpendicular grooves centrally in the lens. The sculpt depth variesbetween 60% in normal cataracts and about 80% in extremely brunescentcataracts. The sculpture length is held within the boundaries given bythe capsulorhexis. As the next step, either the phaco tip and anadditional hook are used to separate the lens into quadrants or specificcracking forceps are used. This separation is then propagated all theyway out to the edge of the lens. Then, the single quadrants arephacoemulsified and simultaneously pulled out of their location. Littleor no tissue is left behind in the outer rims of the lens.

In laser cataract surgery, the lens is preconditioned by the laser sothe separation of the lens into quadrants is simplified. But the accessof the laser is limited and apertured to the opening size of the irisplus an additional safety margin. So the laser actually cannotcompletely place cutting lines across the entire length of the lens.Therefore, there is still the need for the surgeon to manually break theremaining uncut areas and separate the lens into the quadrants.Additionally, because the laser cuts are so narrow in width, it can bedifficult for the surgeon to insert a surgical instrument into the cutsfor splitting the lens.

The pulse energies used to enable laser facilitated cataract surgery istypically twice the optical breakdown threshold of the laser pulse used.For femtosecond lasers this is typically in the range of 1 to 20 microJoules. This allows the efficient generation of cuts within the lens.The mechanical side effects which are caused by the cavitation bubblesgenerated by the laser pulses are a function of the pulse energy, andthe magnitude of this effect is driven by the pulse energy. For 1-20 μJpulses, the size of the bubbles is limited to about 10-200 μm. Thislimited damage range of the cavitation bubbles enables the highlyprecise micromachining of the lens tissue.

Nanosecond laser pulse induced cavitation has been used in ophthalmologyfor the removal of posterior secondary cataracts after lensimplantation. The pulse energies used are typically 1-2 mJ, so about afactor of 100 to 1000 higher than the femtosecond laser pulse energiesused for cataract surgeries. The size of the induced cavitation bubblesare in the order of 1-2 mm. In early in-vitro studies, the nanosecondlaser was also used within the lens in an attempt to emulsify cataractwithin the crystalline lens. (Intraocular photodisruption withpicosecond and nanosecond laser pulses: tissue effects in cornea, lens,and retina. Vogel A, Capon M R, Asiyo-Vogel M N, Bimgruber R., InvestOphthalmol Vis Sci. 1994 June; 35(7):3032-4) It was evident that hugemechanical side effects of the nanosecond laser pulses made thisapproach impractical for cataract emulsification.

It has been discovered that combining low power pulses to generate cutsin the lens, followed by higher power pulses directed to the previouslyformed cuts (using co-registered patterns for both), provides animproved technique and device for preconditioning and completelyseparating the lens segments without further manual surgeonintervention. The low energy pattern of pulses (on the order of 1 to 20micro Joules per pulse) cuts (scribes) the lens to divide it into (stillattached) segments, and the high energy pattern of pulses (on the orderof 100 μJ to 3 mJ per pulse, generated by example from a Q-switched YAGlaser), which are registered to the first pattern of low energy pulses,drives the precut areas apart even though the co-registered patterns donot reach the edge of the lens.

In the preferred non-limiting embodiment, the low energy pulses arepositioned close together or even partially overlapping to effectivelycreate cuts (scribe lines) deep but not all the way through thethickness of the lens to divide it into segments (in this case, 4quadrants). Then, high energy pulses (preferably spaced further apartfrom each other than the low energy “cutting” pulses) are applied to thesame scribe lines (i.e. the patterns for the low and high energy pulsesare co-registered to each other using the pattern laser control systemdescribed above) to separate the segments from each other.

FIG. 20 illustrates the application of low power pulses (depicted assmall circles, 700, in FIG. 20) applied to the lens (69) in a pattern oftwo orthogonal lines (710, 712), which results in two cuts that dividethe lens into four quadrants (702, 704, 706, 708). Similarly, FIG. 21illustrates the application of high power pulses (depicted as largercircles, 714, in FIG. 21) applied in a similar orthogonal line (716,718) pattern (i.e., similar to the cuts formed by the low power pulses),which separates the four quadrant segments (720, 722, 724, 726) of thelens (69) from each other. The high power pulses (714) are shown withgreater separation than the lower power pulses (element 700 of FIG. 20),which is preferable but not necessary. The high power pulses (714) arealso shown in FIG. 21 with greater size, to reflect their greater pulseenergy (and commensurately larger cavitation bubble dimension) relativeto the low power pulses (element 700 of FIG. 20). The physical size ofthe high power pulses on the lens can match that of the low powerpulses, and can vary. Lower and higher, as well as low and high energypulses as used herein describes not a fixed pulse energy for a set ofpulses, but the distinction between the nominal energies of the two setsof pulses. This further distinguishes their purpose.

It is also important to note that the underlying pattern of lower energypulses leaves behind a layer of opacity that provides further shieldingof the retina from the higher energy pulses delivered afterwards. Thisshielding offers an increased margin of patient safety. Using lowerenergy pulses to create a nominally contiguous segmentation patternwithin the lens, but not completely throughout the lens volume providesthe ideal basis for the present invention.

Referring to FIGS. 22 and 23, two treatment paradigms are illustratedusing a side view of a lens (69) to facilitate the depiction of depthdimensions within the lens (69). Referring to FIG. 22, in oneembodiment, the majority of the lens (69) is segmented using the finerand less mechanically intrusive lower energy pulses (700), while theuppermost portion (i.e., most anterior to the face of the patient) ofthe cataractous lens is left untreated. Following that, the higherenergy pulses (714) may be brought to bear on that uppermost portion ofthe lens segmentation and force the segments to further divide. The sameconvention described above for illustrating relative pulse energy (i.e.,in FIGS. 20 and 21) is applicable in FIGS. 22 and 23.

Similarly, higher energy pulses (714) may be used at selected points inthe lens (69) segmentation process/pattern to provide piecewise enhancedseparation, such as is shown in the embodiment of FIG. 23.

This makes the segments easier to remove without requiring too many highenergy pulses, thus attempting to minimize the overall energy requiredto effectively segment a lens while also commensurately limiting theamount of gas liberated during the photoablation process. To furtherlimit the possible iatrogenic effects of such gas, the lens may besegmented using higher energy pulses only after the anterior capsule hasbeen incised to provide a means for the otherwise trapped gases toescape. This limits the chances of capsular rupture.

Furthermore, imaging system 71 and/or OCT system 100 of FIG. 1 may beemployed to provide feedback on the segmentation process by monitoringbubble creation and tissue displacement. In this way the signalsprovided by the imaging system may be used as input to ControlElectronics 300 via IO 302 to determine the extent of the bubble createdand/or the amount of actual tissue separation. As an example of anon-limiting embodiment, Control Electronics 300 may be configured todiscontinue the use of higher energy pulses once the prescribed level oftissue separation has been detected. Likewise, tit may continue the useof higher energy pulses until said level is achieved. The use of higherenergy pulses may not be required if the system detects adequateseparation through the use of lower energy pulses alone. Alternatively,the pulse energy may be increased if the abovementioned system(s) do notdetect sufficient tissue segmentation. Alternate methods of assessingthe tissue separation may also be employed, such as a confocalback-reflectance configuration using the treatment beam itself, or aprobe beam such as that provided by aim beam 202.

The laser system that provides the higher pulses may be the same as thatproviding the lower energy pulses, but could also be a different anddistinct source that is interleaved into the scanning system. As such,it should have its own beam train (at least to a common point) andsafety shutter to provide for safe operation. Although thisconfiguration is not shown the attached drawings, the concepts arenevertheless identical. For example, a non-limiting embodiment may bedescribed by referring to FIG. 1 with the added functionality of UFLight Source 4 providing both high and low energy pulses. This may beaccomplished by commanding those energies from UF Light Source 4, oralternately by actively controlling the level of attenuation usingController 300 of fixed output using half-wave plate 8 and polarizer 10via IO 302. Alternately, a pattern may be completed at a lower energysetting and then repeated at a higher energy setting to provide for theinitial incision and the subsequent segment separation. Thisoptomechanical segment separation provides for easier target tissuesegment separation, which in turn makes surgical manipulation simplerand material removal more time and energy efficient. An alternateembodiment of comprises the use of a second pulsed light source. It maybe combined using the same scheme as described in FIG. 1 regarding thecombination of OCT beam 114 and UF beam 6 and/or aim beam 202 usingbeamcombiners 34 and 126, respectively. Alternately, independentlydirecting them into the scanning assembly, and interleaving them maycombine these separate beams. This is similar to the opticalmultiplexing described in U.S. patent application Ser. No. 11/523,159,which is incorporated herein by reference. A system further configuredto accommodate an independent higher pulse energy light source, such asa Q-Switched Nd:YAG laser, may be added to that of FIGS. 1, 3 and 4, asdescribed above.

It is to be understood that the present invention is not limited to theembodiment(s) described above and illustrated herein, but encompassesany and all variations explicitly and implicitly derived therefrom. Forexample, the lens conditioning may be made in multiple steps, with thecapsulotomy occurring between them to accomplish the intended goal.Although not shown in the figures, multiple imaging steps can also beemployed in between treatment steps to account for any changes inposition and/or size due to treatment and further insure the accuratedisposition of laser energy in the target tissue.

What is claimed is:
 1. A method for cataract surgery on an eye of apatient, comprising: scanning a first focus position of a first pulsedlaser beam at a first pulse energy of between one-half microjoule and 50microjoules in a first scanning pattern to photodisrupt a first tissuestructure portion with a plurality of pulses of the first laser beam toform an incised surface; and after scanning first focus position of thefirst laser beam in the first scanning pattern, scanning a second focusposition of a second pulsed laser beam having a second pulse energybeing between 50 microjoules and 5,000 microjoules in a second scanningpattern that is co-registered to the first scanning pattern to disposethe second focal position on the incised surface for a plurality ofpulses of the second laser beam to further photodisrupt the same firsttissue structure portion with the second laser beam to further separatesegments of the first tissue structure along the incised surface,wherein the pulses of the first laser beam scanned in the first scanningpattern have a first pulse duration between 100 femtoseconds and 10picoseconds, and the pulses of the second laser beam scanned in thesecond scanning pattern have a second pulse duration between 10picoseconds and 10 nanoseconds and is longer than the first pulseduration.
 2. The method of claim 1, wherein the first tissue structureportion is a portion of a crystalline lens of the eye.
 3. The method ofclaim 1, wherein the controller is operatively coupled to the first andsecond laser sources, and configured to control the first and secondpulse energies.
 4. The method of claim 1, wherein the first scanningpattern is configured to divide the lens into two or more discretesegments.
 5. The method of claim 1, wherein the first scanning patterncomprises a three-dimensional pattern wherein two or more pulses aretargeted for two or more different depths within the targeted tissuestructure portion.
 6. The method of claim 1, wherein the pulses of thefirst laser beam scanned in the first scanning pattern have asubstantially distinct range of pulse energies relative to the pulses ofthe second laser beam scanned in the second scanning pattern.
 7. Themethod of claim 6, wherein the pulses of the first laser beam scanned inthe first scanning pattern have a pulse energy of 1 microjoule to 20microjoules and the pulses of the second laser beam scanned in thesecond scanning pattern have a pulse energy of 100 microjoules to 3millijoules.
 8. The method of claim 7, wherein the pulses of the firstlaser beam scanned in the first scanning pattern are directed to adeeper portion of the targeted tissue structure portion than the pulsesof the second laser beam scanned in the second scanning pattern.
 9. Themethod of claim 1, wherein the second scanning pattern comprisesincreased spacing between the focus position of adjacent pulses of thesecond laser beam relative to spacing between the focus position ofadjacent pulses of the first laser beam in the first scanning pattern.10. A method for cataract surgery on an eye of a patient, comprising:scanning a focus position of a first pulsed laser beam having a firstpulse energy of between one-half microjoule and 50 microjoules in afirst pattern so as to photodisrupt tissue with a plurality of pulses ofthe first laser beam to incise a plurality of intersecting cut planeswithin a lens; and after scanning the focus position of the first laserin the first pattern, scan the focus position of a second pulsed laserbeam having a second pulse energy being between 50 microjoules and 5,000microjoules in a second pattern that is co-registered with the firstpattern to dispose the focus position of the second laser on at leastone of the cut planes for a plurality of pulses of the second laser beamso as to further photodisrupt tissue along at least one of the cutplanes incised by the scanning of the first laser to further separatesegments of the tissue along at least one of the cut planes incised bythe first laser, wherein the pulses of the first laser beam scanned inthe first scanning pattern have a first pulse duration between 100femtoseconds and 10 picoseconds, and the pulses of the second laser beamscanned in the second scanning pattern have a second pulse durationbetween 10 picoseconds and 10 nanoseconds that is longer than the firstpulse duration.
 11. The method of claim 10, wherein the laser lightsource includes a first laser source configured to deliver the firstlaser beam and a second laser source configured to deliver the secondlaser beam.
 12. The method of claim 10, wherein the second patterncomprises increased spacing between the focus positions of adjacentpulses of the second laser beam relative to spacing between the focuspositions of adjacent pulses of the first laser beam in the firstpattern.
 13. The method of claim 10, wherein the pulses of the firstlaser beam scanned in the first scanning pattern are directed to adeeper portion of the targeted tissue structure portion than the pulsesof the second laser beam scanned in the second scanning pattern.
 14. Amethod for cataract surgery on an eye of a patient, comprising: scanninga focus position of a first pulsed laser beam having a first pulseenergy of between one-half microjoule and 50 microjoules in a firstpattern so as to photodisrupt tissue with a plurality of pulses of thefirst laser beam to incise a plurality of intersecting cut planes withina lens; and after scanning the focus position of the first laser beam inthe first pattern, scanning a focus position of a second pulsed laserbeam, for a plurality of pulses of the second laser beam having a secondpulse energy greater than the first pulse energy of between 50microjoules and 5,000 microjoules in a second pattern that isco-registered with the first pattern so as to further photodisrupttissue along at least one of the cut planes incised by the scanning ofthe first laser beam to further separate segments of the tissue along atleast one of the cut planes incised by the scanning of the first laserbeam, wherein the pulses of the first laser beam scanned in the firstscanning pattern have a first pulse duration between 100 femtosecondsand 10 picoseconds, and the pulses of the second laser beam scanned inthe second scanning pattern have a second pulse duration between 10picoseconds and 10 nanoseconds and is different than the first pulseduration.
 15. The method of claim 14, wherein the laser light sourceincludes a first laser source configured to deliver the first laser beamand a second laser source configured to deliver the second laser beam.16. The method of claim 14, wherein the second pattern comprisesincreased spacing between the focus positions of adjacent pulses of thesecond laser beam relative to spacing between the focus positions ofadjacent pulses of the first laser beam in the first pattern.